Genetic diversity of two selected antigen loci in Babesia gibsoni Asian genotype obtained from Japan and Jeju island of South Korea

Previous reports have shown that the secreted antigen 1 of Babesia gibsoni (BgSA1) and the thrombospondin-related adhesive protein of B. gibsoni (BgTRAP) are promising diagnostic reagents and vaccine candidates. Therefore, we determined the extent of nucleotide sequence variation in the BgSA1 and BgTRAP genes, obtained from eight isolates of B. gibsoni got from clinically infected dogs in geographically distinct areas of Japan and one isolate from Jeju island of South Korea. Sequence analyses have revealed that nucleotide diversity is lower in BgSA1 than that in BgTRAP. The mean number of non-synonymous (dn) nucleotide substitutions was significantly greater than that of synonymous (ds) ones per site in region II of BgTRAP. Overall, the results predict more allele-specific immunity to BgTRAP than that to BgSA1, which could be useful in designing and testing efficacy of diagnostic reagents as well as vaccine candidates for the B. gibsoni isolates from Japan and Jeju island of South Korea.